This invention relates to an external output video signal processor for carrying out external output of the video signal with a predetermined p-p value. The fundamental configuration of an external output video signal processor currently used conventionally is shown in FIG. 3. The DC component of a video signal output from system controller 10 is cut with coupling capacitor 30. The video signal is taken into clamping circuit 23 (for example, see Japanese Unexamined Patent Publication No. 46443/1995) of video signal processing circuit 20a which consists of a microchip and it's continuous current is regenerated. It is sent to latter part processing circuit 22, and is amplified (p-p value) in the part. After being adjusted, it is output outside. Since the video signal which is output from latter part processing circuit 22 is determined to set to 1.0 Vpp when it is terminated by 75-ohm resistance, the output swing (p-p value) usually serves as 2.0 Vpp.
FIG. 4 is a figure showing the configuration of an external output video signal processor in which system controller 10a of FIG. 3 is shown in more detail. The video signal output by DSP 11 of system controller 10a in current is converted into voltage by resistance 12, matched with impedance by impedance conversion circuit 13, and input into coupling capacitor 30.
If video signal is made to input into latter part processing circuit 22 of video signal processing circuit 20a as it is when the reference level of video signal output from system controller 10a is not being fixed, or when sync. tip is not the optimal level, crushing occurs in the top or the bottom of the signal wave form, which are output from the latter part processing circuit 22, and when the video signal is reproduced, deterioration of image quality will be caused.
Then, in order to prevent distortion of the signal wave form output from this latter part processing circuit 22, coupling capacitor 30 and clamping circuit 23 are formed as mentioned above. With coupling capacitor 30, DC component of output is cut and only the Alternating Current component is extracted. Continuous current regeneration of this is input and carried out to clamping circuit 23. By doing in this way, sync. tip level and pedestal level are fixed to predetermined level, and the indispensable dynamic range is retained.